In Situ-Fabricated In₂S₃‑Reduced Graphene Oxide Nanosheet Composites for Enhanced CO₂ Electroreduction to Formate

The use of renewable electricity to catalyze carbon dioxide reduction is a promising method for CO₂ utilization. However, the lack of highly efficient catalysts for CO₂ reduction seriously limits its industrial applications. As a prototype, an ultrathin indium sulfide nanosheet (In₂S₃ NS) was synthesized and fabricated in situ on reduced graphene oxide (RGO) to obtain an In₂S₃–RGO composite. Induced by the two-dimensional (2D) structure of graphene oxide, the thickness of the In₂S₃ NSs was reduced from 30.2 to 3.9 nm. Simultaneously, the (440) plane of In₂S₃ NSs was preferentially grown parallel to the graphene plane, which was proven to possess a higher selectivity in catalyzing CO₂ electroreduction to formate than the (111) and (311) planes by density functional theory calculations. Attributed to the 2D structure and full exposure of the (440) planes, a large electrochemically active surface area and high density of optimum active sites were both realized on the In₂S₃–RGO hybrids, leading to 91% faradaic efficiency of formate at −1.2 V versus The reversible hydrogen electrode in 0.1 M KHCO₃ is 3.5 times that of bulk In₂S₃ (26%). Our work provides an effective way to prepare 2D transition metal catalysts with controllable crystal face exposure for specific reactions.